QuakeScout
Magnitude4.8

Reviewed by USGSTonga49y ago

M4.8 earthquake 278 km SSW of ‘Ohonua, Tonga

Thursday, June 30, 1977, 03:14:09 UTC · 23.778°S, 175.602°W

A magnitude 4.8 earthquake struck 278 km SSW of ‘Ohonua, Tonga on Thursday, June 30, 1977, 03:14:09 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M4.9 on June 29, 1977.

Magnitude
4.8
Light · mb
Depth
33 km
Shallow
Felt reports
0
Did You Feel It?
Est. shaking
—
No ShakeMap
PAGER alert
None
Not issued
Tsunami
No flag
USGS feed

Outlined circle: this earthquakeDashed circle: 50 km aftershock search area

In context

How big was it, and why here?

Energy released

239 tons of TNT

That is about 1/63 of the Hiroshima bomb. A magnitude 5.0 releases about 2 times more energy.

Tectonic setting

6 km

from the nearest mapped plate boundary, between the Kermadec and Tonga plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.

Depth: shallow

33 km

Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.

Did You Feel It?

Where it was felt

No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.

I felt it — report to USGS ↗

USGS PAGER estimate

Who was exposed to shaking

USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.

After the main event

Aftershocks within 50 km

USGS lists 1 M2.5+ earthquake within 50 km in the following 30 days; the largest was M4.4 on July 13, 1977. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M4M51h6h1d3d7d14d30dMainshock M4.8
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 4.4269 km S of ‘Ohonua, Tonga49y ago · 37 km E of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 204 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 7.8south of TongaOctober 11, 1975 · 133 km S of this epicenter
  2. 7.6south of the Fiji IslandsDecember 18, 1963 · 166 km SW of this epicenter
  3. 7.4south of TongaMarch 18, 1905 · 233 km E of this epicenter
  4. 7.3south of the Fiji IslandsJanuary 20, 1970 · 288 km SW of this epicenter
  5. 7.2south of the Fiji IslandsNovember 24, 1960 · 120 km SW of this epicenter
  6. 7.0south of TongaJanuary 10, 1956 · 297 km S of this epicenter
  7. 6.8Tonga regionJune 22, 1977 · 105 km N of this epicenter
  8. 6.7south of the Fiji IslandsSeptember 8, 1920 · 104 km SW of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 8 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 1 recorded deaths. The most severe:

  1. 1977M7.2

    Tonga Trench

    22 Jun 1977 · 105 km away · intensity IV

    1 death$1 million damagetsunami

  2. 1937M8.1

    Fiji Islands

    16 Apr 1937 · 291 km away

  3. 1975M7.8

    S Of Tonga

    11 Oct 1975 · 133 km away

  4. 1963M7.5

    Tonga Trench

    18 Dec 1963 · 152 km away

    tsunami

  5. 1977M7.2

    Tonga Trench

    10 Oct 1977 · 232 km away

    tsunami

  6. 1956M7.0

    Tonga Islands

    10 Jan 1956 · 250 km away

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers

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